In a deal worth approximately $50 million, Mobile Theory stands out as Opera's biggest acquisition to date. The acquisition of 4th Screen Advertising is worth roughly $14.5 million.

Opera already has advertising solutions directed at featurephone and smartphone operating systems (i.e. iOS, Android, BlackBerry, etc.), and company reps admit that originally, Opera's mobile ad business was all on the supply side.

With these new assets, Opera is getting a play on the demand side as well as a larger presence on an international level.

Specifically, the London-based 4th Screen Advertising is touted as "a leading premium mobile advertising network focused on serving the European mobile advertising markets," giving the San Mateo, Calif.-based Opera a much firmer footprint across the Atlantic.

Mobile Theory, based in San Francisco, already has a strong hold over the U.S. with offices in New York City, Chicago, Los Angeles and Seattle.

Opera will be using its new resources for the purposes of expanding solutions mobile advertisers and publishers across all mobile platforms as well as better monetize traffic on the Opera Mini and Opera Mobile browsers.

Rachel King is a staff writer for CBS Interactive based in San Francisco, covering business and enterprise technology for ZDNet, CNET and SmartPlanet.
She has previously worked for The Business Insider, FastCompany.com, CNN's San Francisco bureau and the U.S. Department of State. Rachel has also written for MainStreet.com, Irish Americ...
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